Chitin whisker liquid crystal hydrogel embedded with polyacrylic acid templating osteoid-like Bouligand structure for...

Sophisticated layered structure and organic/inorganic composition endow lamellar bone with exceptional mechanical properties, which are originated from the mineralization of osteoid with liquid crystal (LC) Bouligand structure under polyanion microenvironment. However, there are few reports focusing on the mechanism of LC phase guided mineralization, and constructing suitable LC models to explore osteoid mineralization remains a challenge. Here, we propose a novel LC hydrogel with Bouligand structure and rich in -COOH groups to simulate osteoid mineralization. Specifically, chitin whiskers (CHWs) co-assemble with polyacrylic acid (PAA) to form osteoid-like LC phase, which is crosslinked to prepare LC hydrogel with Bouligand structure. Using this LC hydrogel as a template to guide the mineralization of PAA-stabilized amorphous calcium phosphate (ACP), a bone ECM-like organic/inorganic composite is achieved. Due to the strengthening/toughening effect of Bouligand structure and formed calcium phosphates, the composite exhibits excellent mechanical properties. Creatively, LC template achieves effective internal mineralization under the synergetic guidance of Bouligand structure and PAA, moreover, there is differential mineralization inside/outside the LC template, which well mimics natural bone. This study first reveals the biomineralization mechanism and synergistic effect guided by Bouligand structure and PAA, providing an innovative idea for exploring the formation of lamellar bone.